Howdy, all 
One of our community members @gsmith recently pointed another community member to a repo that Graylog maintains and is full of basic pipeline examples. I’ve personally used this repo quite often when I’m crafting a pipeline. You can find it here https://github.com/Graylog2/graylog-plugin-pipeline-processor/tree/master/plugin/src/test/resources/org/graylog/plugins/pipelineprocessor. There are three directories that have NUMEROUS examples. Hopefully you find this as useful as I have!